About 10-30% on the LSI 9341 (flashed to SAS9300 generic to avoid INT15 issues). It was 60-75% with software onboard raid0 with just 3 drives, I imagine it gets even worse the more you add.
With INT13 (diff int) boot support disabled the controller doesnt add much longer to reboots.. about 20sec maybe.
MRFS, the reason I wanted a controller that might do 6-7GB/s is I wanted to future proof 12Gb/s support later, so I could use cheap drives now and in a couple of years upgrade to hopefully cheap excess enterprise 12Gb drives. On a card like the 9341, its 4 channels x 12Gb x 2 Ports right? So ignoring the PCIe interface, its max connectivity would be limited to 2x 6GByte..?